Magnetic core



Dec. 14, 1948.

erwtor:

Ifiv Gare th G. Somervi I le,

His Attrney.

Patented Dec. 14, 1948 PATENT ,oFncE MAGNETIC CORE Gareth G. Somerville, Plttsileld, Mam, alsi gnor to General Electric Company, a corporation of New York Application January 1a, 1947, Serial No. 722,839 I 2 Claims. 1

This invention relates to magnetic cores and more particularly to improvements in three phase magnetic cores for stationary induction apparatus.

In an application, Serial No. 722,843, filed J anuary 18, 1947, in the name of Cecil G. Dunn, and assigned to the present asslgnee, there is described a three phase core consisting of three radially laminated U-shaped core portions whose corresponding ends are' joined by interleaved magnetic inserts of at least two different shapes. The magnetic material of the laminations and of the 'inserts has a most favorable magnetic direction, that direction in the laminations coinciding with their length.

In accordance with this invention, there is provided an improved core of the Dunn type which is characterized by having geometrically similar magnetic inserts which have a symmetrically staggered orientation relative to their most favorable magnetic direction. The preferred shape of these inserts is triangular.

An object of the invention is to provide an improved three phase core of the bent strip steel p Another object of the invehtion is to provide an improved center joint for Y type yoke, three phase magnetic cores of the bent strip steel type.

The invention will be better understood from the following description taken in connection with the accompanyin drawing and its scope will be pointed out in the appended claims.

Referring now to the single figure of the accompanying drawing, which is a perspective view of a preferred embodiment of the invention, three generally U-s-haped core portions, l,.2 and I are shown. These portions may be duplicates of each other and, as shown, they preferably consist of a central relatively long straight core leg portion 4 and generally right angularly disposed shorter yoke portion 5. They are composed of nested U-shaped laminations of magnetic material such as cold rolled silicon strip steel which has a most favorable magnetic direction in the direction of rolling which in the case of the core portion coincides with the length of the lamination. The ends of the yoke parts i of the core portions may conveniently be cut square, as shown. Preferably, the ends of the yoke parts I have an alternate tongue and groove configuration which can conveniently be provided by lengthwise offsetting or staggering of the laminations making up each core portion.

The core portions may be made by winding a strip of magnetic steel on a suitably shaped mandrel and then cutting it in two places and rearranging the laminations to provide the desired staggered. configuration of the ends, or the core portions may be formed by cutting magnetic 5 pieces of the desired length from a longer strip of the magnetic material and then assembling strips of progressively different length into packets which are bent in any suitable manner into the shape shown. In either case, the core in portions should be given a strain relief anneal before they are assembled into the final three phase core.

Joining the corresponding ends of the three core portions are alternately disposed small and large triangular inserts 6 and I which are fitted into the spaces between the corresponding ends of the laminations at both ends thereof. In this manner, the butt joints between the ends of the laminations in the U-shaped members and the sides of the triangular inserts are staggered or overlapped so as to provide low reluctance magnetic Joints.

, The material from which the inserts 6 and I are made is preferably that from which the laminations of the U-shaped core portions are made and the triangular members are so cut that their most favorable magnetic direction is parallel to one side thereof as indicated by the arrows shown thereon. As shown, there are three diflere'itsets of arrows displaced 120 from each other, one arrow, for example, illustrating the grain direction of the top insert 6, the next arrow indicating the grain direction of the next uppermost insert 1, and the last arrow indicating the grain direction of the third insert 6. This'cycle is then repeated. In this manner, the magnetic directions of the inserts are symmetrically oriented so that the triangular center portion of the three phase core yoke has equally good magnetic properties 40 in three directions disposed 120 with respect to each other.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the spirit of the invention and it is therefore aimed in the appended claims to cover all such changes and modifications as fallwithin the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A three phase magnetic core comprising, in combination, three generally U-shaped core portions made of nested curved U-shaped laminations. each having a most favorable magnetic direction coinciding with its length; the ends of the core portions having an alternating tongue and groove configuration produced by ofi'setting the ends of the iaminations, and magnetic inserts fitted into the grooves 0! corresponding ends of said portions for Joining them together. said inserts each having a most favorable magnetic direction, successive inserts having their most favorable magnetic direction progressively rotated at 120.

2. A three phase magnetic core comprising, in combination, three U-shaped core portions made 0! nested curved, square ended U-shaped laminations, having a most iavorable magnetic direction coinciding with their length, the ends of the core portions having an alternatin team and groove configuration produced by lengthwise offsetting of the ends of the laminations, and triangular magnetic inserts fitted into the grooves of corresponding ends oi. said portions for Joining them together, said inserts each having a most favorable magnetic direction parallel to one side. said inserts being so oriented that substantially equal numbers of them have their most favorable magnetic direction symmetrically disposed angularly with respect to each other.

GARETH G. SOMERVILLE.

No references cited. 

